package com.sgj.forkjoin;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.ForkJoinTask;
import java.util.concurrent.RecursiveTask;

/**
 * @Author: Guoji Shen
 * @Date: 2021/8/11 10:07
 */
public class ForkJoinDemo {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        // 创建对象
        MyTask myTask = new MyTask(0, 100);

        // 创建分支合并池对象
        ForkJoinPool forkJoinPool = new ForkJoinPool();
        ForkJoinTask<Integer> forkJoinTask = forkJoinPool.submit(myTask);

        // 获取最终合并之后的结果
        Integer result = forkJoinTask.get();
        System.out.println(result);

        // 关闭池对象
        forkJoinPool.shutdown();
    }
}

class MyTask extends RecursiveTask<Integer> {

    // 拆分差值不能超过10,计算10以内的运算
    private static final Integer VALUE = 10;

    /**
     * 拆分开始值
     */
    private int begin;

    /**
     * 拆分结束值
     */
    private int end;

    /**
     * 返回结果
     */
    private int result;

    public MyTask(int begin, int end) {
        this.begin = begin;
        this.end = end;
    }

    // 拆分和合并的过程
    @Override
    protected Integer compute() {
        // 判断相加两个数值是否大于10
        if ((end - begin) <= VALUE) {
            // 相加
            for (int i = begin; i <= end; i++) {
                result = result + i;
            }
        } else {
            // 进一步拆分
            // 获取数据中间值
            int middle = (begin + end) / 2;

            // 拆分左边
            MyTask task01 = new MyTask(begin, middle);

            // 拆分右边
            MyTask task02 = new MyTask(middle + 1, end);

            // 调用方法拆分
            task01.fork();
            task02.fork();

            // 合并结果
            result = task01.join() + task02.join();
        }
        return result;
    }
}